The Human Subjects/Data Analysis (HSDA) Core will support Program research efforts through its three subcomponent Units. The Human Subjects Unit will recruit and screen all volunteer subjects and provide medical oversight of them during all experimental sessions. The Data Analysis Unit, in conjunction with personnel from Core C and Projects 1 to 4, will conduct the statistical analyses of all data gathered by those Program components. It will also conduct the statistical testing of the Program-global hypotheses. The Model Analysis Unit will conduct the inverse dynamics biomechanical model analyses needed in Projects 2, 3 and 4.